linux-kernel - Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

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Date:	Wed, 16 Jan 2013 15:25:57 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, pjones@...hat.com, hpa@...or.com,
	dhowells@...hat.com, jwboyer@...hat.com,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-security-module@...r.kernel.org,
	Ryan Ware <ryan.r.ware@...el.com>
Subject: Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

On Wed, 2013-01-16 at 14:47 -0500, Vivek Goyal wrote:
> On Wed, Jan 16, 2013 at 02:37:24PM -0500, Mimi Zohar wrote:
> > On Wed, 2013-01-16 at 13:57 -0500, Vivek Goyal wrote:
> > > On Wed, Jan 16, 2013 at 01:45:12PM -0500, Mimi Zohar wrote:
> > > 
> > > [..]
> > > > > Given the fact that signatures are stored in extended attributes, to me
> > > > > the only way to sign executables in current IMA framework would to be
> > > > > prepare file system image at build server and ship that image. And
> > > > > then installer simply mounts that image (after making sure that proper
> > > > > verification keys have been loaded in kernel).
> > > > 
> > > > That is one scenario.  Another scenario is to update packages to include
> > > > extended attributes and to write those extended attributes on
> > > > installation.
> > > 
> > > Ok, that's the point I am missing. So I can sign a file and signatures
> > > are in a separate file. And these signatures are installed in extended
> > > attributes at file installation time (IOW rpm installation time) on
> > > target.
> > > 
> > > If all this works, this sounds reasonable so far. Except the point of
> > > disabling ptrace and locking down memory. 
> > > 
> > > So what's the state of above work. Is there something I can play with.
> > 
> > Sorry, I'm not sure of the RPM implementation details of where/how the
> > signatures are stored in the package, nor of the status of these
> > changes.  Perhaps someone else on the mailing list knows.
> 
> So irrespective of fact how RPM does it. What are basic commands/steps to
> generate signature of a file and how to store it later in an extended
> attribute?

evmctl calculates and writes out the 'security.evm' and 'security.ima'
extended attribute.  The ima-evm-utils package README contains some
directions for getting started.  We should probably move this thread to
the linux-ima-user mailing list.

thanks,

Mimi


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